This study focuses on the influence of roughness lay directionality on micropit crack formation, using a computational approach. A mixed lubrication model is implemented to find the surface tractions, which are used in a stress model to compute the near surface stress concentrations. With the stress amplitudes and means determined, the crack formation lives are assessed according to a fatigue criterion. It is found when the roughness lays of the two surface are parallel to the rolling direction and are out-of-phase, the resulted micropitting area percentage is minimum. The most severe micropitting activity is observed on the surface whose roughness lay is parallel to the rolling direction, while the roughness lay of its counterpart is normal to the rolling direction.